Spot on, Rudram. Flowers touching the glass means that natural condensation, perhaps in the night, causes cells to rot away. And the mechanical damage, cracking, from some kind of accident.
But a good friend in the orchid trade taught me this lesson many years ago. Ask yourself, what are you buying, a bunch of flowers to give you pleasure for a week or two ? Or a plant which will give you pleasure year after year : if the latter, then, cut off damaged flower spikes - ok you lose the pleasure now, but the plant can then start growing on to give you more pleasure next year. They don't grow while they are carrying this year's flowers ( except in th case of big strong plants growing under perfect conditions).